A good starting point is to list all of the nations that were represented at the peace conference in 1919.

These were 32 allied and associated powers, either as voting members or as observers. This number consisted of:

  • The thirty sovereign nations that declared war (see list to follow),
  • Less Montenegro, which was included in the 1919 Jugo-Slav state along with Bosnia, Croatia and Slovenia,
  • Less Newfoundland and
  • Including Czechoslovakia, the Arab state of Hedja, Poland and the 1919 Jugo-Slav state.

The five defeated nations were also allowed to be represented but were excluded from all of the deliberations.

Allies that declared war and engaged in military action: 20 – Australia, Belgium, Brazil, Canada, France, Greece, India, Italy, Japan, Montenegro, Newfoundland, New Zealand, Portugal, Romania, Russia, Serbia, Siam, South Africa, United Kingdom and United States.

Allies that declared war but didn’t engage: 10 – China, Costa Rica, Cuba, Guatemala, Haiti, Honduras, Liberia, Nicaragua, Panama and San Marino.

Allies who broke diplomatic relations with Germany but didn’t declare war: 4 – Bolivia, Ecuador, Peru and Uruguay

Total of the above: 34

Modern nations that were part of combatant allied empires or nations in 1914 and were actively involved in the war in some way:

American ‘Empire’: 1 Philippines

Belgian Empire: 1 Congo

British Empire: 19 Ireland, Bahamas, Belize, Bermuda, Jamaica, Barbados, Zambia, Malawi, Uganda, Kenya, Ghana, Zimbabwe, Egypt, Nepal, Myanmar, Pakistan, Sri Lanka, Bangladesh, Singapore

French Empire: 10 Malagasy, Senegal, Mali, Mauretania, Algeria, Morocco, Tunisia, Cambodia, Laos, Vietnam

Japanese Empire: 3 Korea (2), Taiwan

Portuguese Empire: 2 Angola, Mozambique

Russian Empire:  16 Poland, Belarus, Ukraine, Moldova, Lithuania, Latvia, Estonia, Finland, Armenia, Georgia, Azerbaijan, Kazakhstan, Tajikistan, Uzbekistan, Kyrgyzstan, Turkmenistan

Serbia: 2 Macedonia, Kosovo

Total for this group: 54

Central Powers that declared war:

Austria-Hungary (2), Bulgaria, Germany and Ottoman Empire.

Total for this group: 5

Modern nations that were part of combatant Central Power empires in 1914 and were actively involved in the war in some way:

German Empire: 11 – Namibia, Tanzania, Rwanda, Burundi, Papua New Guinea, Marshall Islands, Palau, Kiribati, Samoa, Togo, Cameroon

Austro-Hungarian Empire: 5 – Slovenia, Czech R., Slovakia, Croatia, Bosnia

Ottoman Empire: 12 – Syria, Palestine, Israel, Jordan, Iraq, Saudi Arabia, Yemen, Oman, Qatar, UAE, Kuwait, Bahrain

Total for this group: 28

Countries that didn’t declare war but were nevertheless actively involved in some way: Albania, Chile, Luxembourg, Mexico, Persia, Vatican

Total for this group: 6

Grand Total 127

This article claims 158.

76 countries sent participants to the 2014 Bastille Day Parade in Paris that also recognized the centennial of the First World War.

James (“Jim”) Patton BS BA MPA is a retired state official from Shawnee, Kansas and a frequent contributor to several WW1 e-publications, including "Roads to the Great War," "St. Mihiel Tripwire," "Over the Top" and "Medicine in the First World War." He has spent many hours walking the WW1 battlefields, and is also an authority on British regiments and a collector of their badges. An Army Engineer during the Vietnam War, he does work for the US World War 1 Centennial Commission and is affiliated with the WW1 Historical Association, the Western Front Association, the Salonika Campaign Society and the Gallipoli Association.